The present invention relates in general to end controlled walkie/rider pallet trucks commonly used for picking stock in large warehouses and, more particularly, to supplemental controllers mounted adjacent the base of forks of such pallet trucks for improved operation of the trucks and including, for example, one or more jog switches and/or twist grips in combination with one or more coast release switches.
A typical walkie/rider pallet truck includes load carrying forks and a power unit having a steerable wheel, a steering control mechanism, a brake including a deadman brake mechanism, an electric traction motor, a storage battery and a platform onto which the operator may step and ride while controlling the truck. The steering mechanism normally has a handle mounted at the end of a movable steering arm with the handle including controls for raising and lowering the forks and rotatable twist grips or comparable devices to control the speed and direction (forward and reverse) of the truck. A switch for reversing vehicle travel direction when traveling in the power unit first or forward direction and a horn switch are also normally provided on the handle.
In stock picking operations, a truck operator typically follows a winding, unidirectional route through the warehouse, picking up stock in a predetermined sequence in order to maximize productivity. The operator normally walks alongside the truck when the distance along the route between picks is short and steps onto the truck platform to ride when the distance between picks is longer, for example twenty or more feet. When the operator is riding on the truck platform, it is desirable for optimum work productivity to move the truck at higher speeds than when the operator is walking beside it. To this end, speed controllers that include high and low speed control circuits are provided.
For movement of the truck, the operator grasps the handle and moves the steering arm into a truck operating range between a generally vertical (up) braking position and a generally horizontal (down) braking position. If the operator releases the handle, the deadman brake mechanism, for example comprising an arm return spring, forces the arm to the up braking position which actuates a vehicle brake, for example a spring-loaded brake, to stop the truck. The operator can also actuate the brake by bringing the steering arm to the down braking position. Thus, the walkie/rider pallet truck may be in either a braking or non-braking mode, depending on the position of the steering arm within specified braking and operating arcs.
Rotation of the twist grips controls movement of the truck: rotation of either grip in one direction causes the truck to move with the power unit leading, the forward direction, while rotation in the opposite direction causes the truck to move with the load carrying forks leading, the backward or reverse direction. Increased rotation of the grip in either direction, when operated in either the walkie or the rider mode, results in an increase in the power supplied to the electric motor causing the truck to move at a higher speed in the corresponding forward or reverse direction.
In addition to the motion control provided by the rotatable twist grips, walkie/rider pallet trucks may also include side or “jog” switches. The jog switches can be used by an operator walking alongside the truck to accelerate the truck to a walking speed of around 3.5 miles per hour (mph) (5.6 kilometers per hour (km/hr)) to move from one stock pick position to the next stock pick position. A single jog switch is normally provided on each side of the handle either on an outer portion of the handle or on an inner, protected portion of the handle. An example of another jog switch arrangement, wherein a pair of switches, one on the outside of the handle and one on the inside of the handle, is provided on each side of the handle and both switches must be activated to move the truck, is illustrated in U.S. Pat. No. 5,245,144 which is entitled WALK ALONG HAND GRIP SWITCH CONTROL FOR PALLET TRUCK which issued on Sep. 14, 1995 to the assignee of the present application and is incorporated herein by reference.
The efficiency of order picking is severely hampered if the brake is activated every time an operator releases the steering arm. Thus, brake override, or coasting, systems have been developed to override the deadman brake mechanism by preventing the steering arm from entering the up braking position when the operator releases the handle/steering arm while walking alongside the truck. During typical operation, an operator may use one of the jog switches to accelerate the truck to walking speed. When approaching a stopping point, the operator releases the jog switch and allows the truck to coast to a stop while the operator moves to an adjacent rack or shelf to pick up an item and place it on a pallet on the forks. The operator plans the coast of the truck so that the pallet on the forks will stop near the operator's position at about the same time that the operator is ready to place the item onto the pallet. After loading the pick onto the truck, the operator again operates one of the jog switches and moves the truck toward the next pick location.
The rate of acceleration and speed of the truck are controlled by switching a jog switch on and off. The coast distance is controlled by controlling the truck's travel speed when the jog switch is released and of course the position of the truck relative to the pick when the jog switch is released. Generally, use of the vehicle brake is not necessary during coasting operation; however, the vehicle brake is available to the operator as needed.
While coasting increases the efficiency of picking operations, after making a pick, the operator still must move from the forks to the handle to once again move the truck using either the twist grips or the jog switches. Over the course of a day's picking operations, the operator may walk a substantial distance just to be able to once again operate the truck after such coasting/picking operations.
Accordingly, there is a need for supplemental jog and/or twist grip walk along controllers for walkie/rider pallet trucks that would substantially reduce if not eliminate the short but numerous walks from the forks of a truck to the control handle of the truck that an operator must now make between closely spaced picks. The supplemental jog and/or twist grip walk along controller would be placed closely adjacent a load backrest associated with the forks so that rather than having to walk to the handle, the operator can control the truck from the vicinity of the load backrest. For jog operation, the operator would be able to move the truck from pick to pick in the coast mode and could apply the brake by releasing the coast mode to enable the deadman mechanism to apply the vehicle brake. For twist grip operation, the operator would be able to move the truck by twisting supplemental twist grips that could be used to plug brake the truck and could also apply the brake by releasing the coast mode to enable the deadman mechanism to apply the vehicle brake. Of course, both supplemental jog and twist grip controls could also be provided.